July-August 1920 Vol. XXVlil, No. |. 



The Journal of Geology" 



Edited By 

 thomas c. chamberlin and rollin d. salisbury 



With the Active Collaboration of 



STUART WELLER ALBERT JOHANNSEN 



Invertebrate Paleontology Petrology 



ROLLIN T. CHAMBERLIN 



Dynamic Geology 



4 



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